An atom-in-molecules and electron-localization-function study of the interaction between O 2 and V x O y + /V x O y ( x = 1, 2, y = 1-5) clusters

Abstract

The most stable structures of V x O y +/V x O y (x=1, 2, y=1–5) clusters and their interaction with O2 are determined by density functional calculations, the B3LYP functional with the 6-31G* basis set. The nature of the bonding of these clusters and the interaction with O2 have been studied by topological analysis in the framework of both the atoms-in-molecules theory of Bader and the Becke–Edgecombe electron localization function. Bond critical points are localized by means of the analysis of the electron density gradient field, ∇ρ(r), and the electron localization function gradient field, ∇η(r). The values of the electron density properties, i.e., electron density, ρ(r), Laplacian of the electron density, ∇2ρ(r), and electron localization function, η(r), allow the nature of the bonds to be characterized, and linear correlation is found for the results obtained in both gradient fields. Vanadium-oxygen interactions are characterized as unshared-electron interactions, and linear correlation is observed between the electron density properties and the V–O bond length. In contrast, O2 units involve typical shared-electron interactions, as for the dioxygen molecule. Four different vanadium–oxygen interactions are found and characterized: a molecular O2 interaction, a peroxo O2 2− interaction, a superoxo O2 − interaction and a side-on O2 − interaction.